porting bazel c++ example to hancho

examples/bazel-cpp-tutorial/README.md

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+This is a copy of Bazel's C++ build tutorial, ported to Hancho for comparison.

examples/bazel-cpp-tutorial/stage1/README.md

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+# Stage 1
+
+This showcases how to build a single file to create a runnable application.
+
+This BUILD file shows that we want to build a C++ binary using the ```cc_binary``` rule provided by Bazel.
+In the ```cc_binary``` rule, name of the binary is specified in ```name``` attribute (in this example, it's ```hello-world```), required source files to be built are provided in ```srcs``` attribute.
+
+```
+cc_binary(
+    name = "hello-world",
+    srcs = ["hello-world.cc"],
+)
+```
+
+To build this example, use
+```
+bazel build //main:hello-world
+```
+
+If the build is successful, Bazel prints the output similar to
+```
+____Loading complete.  Analyzing...
+____Found 1 target...
+____Building...
+Target //main:hello-world up-to-date:
+  C:/tools/msys64/tmp/_bazel_woden/vqeu6v3v/execroot/__main__/bazel-out/msvc_x64-fastbuild/bin/main/hello-world.exe
+____Elapsed time: 0,400s, Critical Path: 0,01s
+```
+
+In the run log above you can see where the executable was built so you can locate it and use it.
+
+You can also get the output path with the bazel cquery command. For
+example, the command below would print the path to the output file. This
+is a useful technique for use in scripts, where you do not want to parse the
+`bazel build` output.
+
+```
+bazel cquery --output=files //main:hello-world
+```

examples/bazel-cpp-tutorial/stage1/build.hancho

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+# ----------------------------------------
+
+compile_cpp = hancho.Config(
+    desc="Compiling C++ {rel(in_src)} -> {rel(out_obj)} ({build_tag})",
+    command="g++ -c {in_src} -o {out_obj}",
+    out_obj="{swap_ext(in_src, '.o')}",
+    in_depfile="{swap_ext(in_src, '.d')}",
+)
+
+link_cpp_lib = hancho.Config(
+    desc="Bundling C++ lib {rel(out_lib)}",
+    in_objs=None,
+    out_lib=None,
+    command="ar rcs {rel(out_lib)} {rel(in_objs)}",
+)
+
+cc_binary = hancho.Config(
+    desc="Linking C++ bin {rel(out_bin)}",
+    command="g++ {in_srcs} {in_objs} {in_libs} -o {out_bin}",
+)

examples/bazel-cpp-tutorial/stage1/main/build.hancho

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+hancho(
+    hancho.cc_binary,
+    name = "hello-world",
+    in_srcs = ["hello-world.cc"],
+)

examples/bazel-cpp-tutorial/stage1/main/hello-world.cc

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+#include <ctime>
+#include <string>
+#include <iostream>
+
+std::string get_greet(const std::string& who) {
+  return "Hello " + who;
+}
+
+void print_localtime() {
+  std::time_t result = std::time(nullptr);
+  std::cout << std::asctime(std::localtime(&result));
+}
+
+int main(int argc, char** argv) {
+  std::string who = "world";
+  if (argc > 1) {
+    who = argv[1];
+  }
+  std::cout << get_greet(who) << std::endl;
+  print_localtime();
+  return 0;
+}

examples/bazel-cpp-tutorial/stage2/README.md

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+# Stage 2
+
+### Library
+
+Here, we introduce the ```cc_library``` rule for building C++ libraries. We have a ```cc_library``` named ```hello-greet``` and its header and source files are defined accordingly.
+```
+cc_library(
+    name = "hello-greet",
+    srcs = ["hello-greet.cc"],
+    hdrs = ["hello-greet.h"],
+)
+```
+
+### Binary
+
+The ```cc_binary``` rule we saw in stage 1 has not changed, except that we now depend on the ```cc_library``` ```hello-greet```.
+```
+cc_binary(
+    name = "hello-world",
+    srcs = ["hello-world.cc"],
+    deps = [
+        ":hello-greet",
+    ],
+)
+```
+
+To build this example, use
+```
+bazel build //main:hello-world
+```

examples/bazel-cpp-tutorial/stage2/main/BUILD

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+cc_library(
+    name = "hello-greet",
+    srcs = ["hello-greet.cc"],
+    hdrs = ["hello-greet.h"],
+)
+
+cc_binary(
+    name = "hello-world",
+    srcs = ["hello-world.cc"],
+    deps = [
+        ":hello-greet",
+    ],
+)

examples/bazel-cpp-tutorial/stage2/main/hello-greet.cc

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+#include "hello-greet.h"
+#include <string>
+
+std::string get_greet(const std::string& who) {
+  return "Hello " + who;
+}

examples/bazel-cpp-tutorial/stage2/main/hello-greet.h

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+#ifndef MAIN_HELLO_GREET_H_
+#define MAIN_HELLO_GREET_H_
+
+#include <string>
+
+std::string get_greet(const std::string &thing);
+
+#endif

examples/bazel-cpp-tutorial/stage2/main/hello-world.cc

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+#include "hello-greet.h"
+#include <ctime>
+#include <iostream>
+#include <string>
+
+void print_localtime() {
+  std::time_t result = std::time(nullptr);
+  std::cout << std::asctime(std::localtime(&result));
+}
+
+int main(int argc, char** argv) {
+  std::string who = "world";
+  if (argc > 1) {
+    who = argv[1];
+  }
+  std::cout << get_greet(who) << std::endl;
+  print_localtime();
+  return 0;
+}

examples/bazel-cpp-tutorial/stage3/README.md

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+# Stage 3
+
+In this stage we step it up and showcase how to integrate multiple ```cc_library``` targets from different packages.
+
+Below, we see a similar configuration from Stage 2, except that this BUILD file is in a subdirectory called lib. In Bazel, subdirectories containing BUILD files are known as packages. The new property ```visibility``` will tell Bazel which package(s) can reference this target, in this case the ```//main``` package can use ```hello-time``` library. 
+
+```
+cc_library(
+    name = "hello-time",
+    srcs = ["hello-time.cc"],
+    hdrs = ["hello-time.h"],
+    visibility = ["//main:__pkg__"],
+)
+```
+
+To use our ```hello-time``` library, an extra dependency is added in the form of //path/to/package:target_name, in this case, it's ```//lib:hello-time```
+
+```
+cc_binary(
+    name = "hello-world",
+    srcs = ["hello-world.cc"],
+    deps = [
+        ":hello-greet",
+        "//lib:hello-time",
+    ],
+)
+```
+
+To build this example, use
+```
+bazel build //main:hello-world
+```

examples/bazel-cpp-tutorial/stage3/lib/build.hancho

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+hancho(
+    hancho.rules.cpp_
+    name = "hello-time",
+    srcs = ["hello-time.cc"],
+    hdrs = ["hello-time.h"],
+    visibility = ["//main:__pkg__"],
+)

examples/bazel-cpp-tutorial/stage3/lib/hello-time.cc

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+#include "lib/hello-time.h"
+#include <ctime>
+#include <iostream>
+
+void print_localtime() {
+  std::time_t result = std::time(nullptr);
+  std::cout << std::asctime(std::localtime(&result));
+}

examples/bazel-cpp-tutorial/stage3/lib/hello-time.h

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+#ifndef LIB_HELLO_TIME_H_
+#define LIB_HELLO_TIME_H_
+
+void print_localtime();
+
+#endif

examples/bazel-cpp-tutorial/stage3/main/BUILD

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+hello_greet = hancho(
+    hancho.cc_library,
+    name = "hello-greet",
+    in_srcs = ["hello-greet.cc"],
+    in_hdrs = ["hello-greet.h"],
+)
+
+hancho(
+    hancho.cc_binary,
+    name = "hello-world",
+    in_srcs = ["hello-world.cc"],
+    in_deps = [
+        hello-greet,
+        hancho.lib.hello-time
+    ],
+)

examples/bazel-cpp-tutorial/stage3/main/hello-greet.cc

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+#include "main/hello-greet.h"
+#include <string>
+
+std::string get_greet(const std::string& who) {
+  return "Hello " + who;
+}

examples/bazel-cpp-tutorial/stage3/main/hello-greet.h

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+#ifndef MAIN_HELLO_GREET_H_
+#define MAIN_HELLO_GREET_H_
+
+#include <string>
+
+std::string get_greet(const std::string &thing);
+
+#endif

examples/bazel-cpp-tutorial/stage3/main/hello-world.cc

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+#include "lib/hello-time.h"
+#include "main/hello-greet.h"
+#include <iostream>
+#include <string>
+
+int main(int argc, char** argv) {
+  std::string who = "world";
+  if (argc > 1) {
+    who = argv[1];
+  }
+  std::cout << get_greet(who) << std::endl;
+  print_localtime();
+  return 0;
+}